This invention relates to the field of ceramics and particularly to the field of solid electrolytes.
Sodium electrolyte materials such as .beta.-Al.sub.2 O.sub.3, B"-Al.sub.2 O.sub.3, and Na.sub.1+x Zr.sub.2 Si.sub.x P.sub.3-x O.sub.12 are ceramics that are capable of conducting electricity because their crystal structures include a sodium ion (Na.sup.+) conductor. Consequently, they are of great interest for use in high energy density, high power density batteries such as sodium sulfur batteries which require conductive ceramics.
Unfortunately, these conductive ceramics are weak, and strength degradation during their use leads to reduced battery lifetime. Surface cracks in the ceramic electrolyte can cause current focusing during battery charging which accellerates the crack growth and leads to degradation. Structural failure of the ceramic due to external stresses can lead to catastrophic sodium sulphur reactions.
Thus, these new high performance batteries need stronger conductive ceramics in order to improve their reliability, increase their current density, and allow the use of thinner-wall electrolytes.